1. Field of the Invention
This invention relates generally to machines and methods for forming metal panels for constructing metal buildings, and more particularly relates to apparatus and methods for forming curved building panels from flat sheet metal material by crimping.
2. Background and Prior Art
It is known in the prior art to construct metal buildings from metal panels which are arched or curved, assembled side-by-side and seamed together. See U.S. Pat. No. 3,902,288 to Knudson. In such buildings the roof panels continue as the side walls of the building and the basic building construction is in the shape of a self-supporting continuous arch or semicircle when viewed from one end. A machine for making the building panels in which U-shaped panels are corrugated or crimped both on the bottom or xe2x80x9cbellyxe2x80x9d and on the sides to create the curvature is shown in U.S. Pat. No. 3,842,647 to Knudson.
An arched building construction in which the walls and roof are completely arched has advantages, but also has a number of limitations. One limitation is the absence of vertical walls which limits the use of vertical space. Users of metal buildings often want vertical walls both for aesthetic purposes as well as to obtain the use of more vertical space near the edges to the building. The basic size and strength of such metal buildings is also limited by wind and live load limitations as established by local and national building codes. A completely arched building must be limited in size in order to prevent overloading as could occur from extensive wind loads produced by hurricanes. However, when the total roof height is reduced to approximately one-fifth of the total building width, hurricane force winds do not affect the building as much because of the reduced frontal area.
Improvements to the above technology are disclosed in U.S. Pat. Nos. 5,249,445 and 5,359,871 to Morello, incorporated by reference herein in their entirety. These patents disclose microprocessor-controlled methods and apparatus wherein metal building panels could be formed by automatically controlling the radius of curvature and wherein the panels may have a straight as well as a curved portion so that metal panel buildings could be constructed with arched roofs and vertical walls. The cited Morello patents disclose the use of hydraulics and microprocessor controlled machinery which forms U-shaped building panels of predetermined length from a coil of sheet metal. The formed panels are then continuously crimped on their side edges for strength and are adjustably curved by crimping the belly of the panel. The crimping is automatically controlled so that building panels may be formed with vertical wall portions and curved or arched roof portions.
A problem in the prior art, however, was the fact that the depth of the crimp on the side edges of the panel remained constant, even as the radius of the panel being curved changed. If the radius of the panel was tight, and the depth of side crimp was shallow, the side walls of the panel buckled due to the excess material not taken up by the crimp. Analogously, if the radius was large or the panel section being formed was straight, and the depth of side crimp was deep, the belly of the panel buckled due to excess material in the belly not taken up by the crimping. Because of the physical distance between the side crimping apparatus and the main crimping apparatus, the simultaneous adjustment of the side and main crimping apparatus caused the length of panel between the side crimper and the main crimper during this adjustment not to have the change in depth of crimp on the side walls, which caused the buckling effect discussed above. Thus, there exists a need in the art for improvement to such apparatus and methods to eliminate the deleterious buckling effects caused by adjustment of the crimping mechanisms during formation of such panels.
The panel crimping apparatus and method of the present invention is unique in that the depth of crimp in the side portion of a metal building panel is controlled by a microprocessor and the side crimping rollers are adjusted independently of the main crimping rollers, according to the radius of panel being curved and the length of panel that has passed through the apparatus. The present invention thus eliminates the problem of metal panel buckling in the prior art when the radius of curvature of a building panel was varied during formation.
The crimping apparatus includes two sets of rotatably mounted panel side portion crimping rollers with the sets mounted vertically with respect to each other and the rollers mounted horizontally on shafts. The outside roller of each set is rotatably mounted on a shaft supported at both ends by stationary bearings. The inside roller of each set is rotatably mounted on a cantilevered shaft supported on only one end by bearings. The bearings of the cantilevered shaft are mounted in a non-stationary sliding block that is movable in the direction of the stationary crimping rollers, thus creating a change in the depth of crimp by changing the distance between the inside roller and the outside roller. The sliding mechanism consists of male and female V-grooved guide bars, with the male guide bar being attached to the sliding block and the female guide bar being attached to a main support plate. Extending through the center of the main plate is a machine screw which is supported on the reverse side of the main plate by a block that houses three angular-contact bearings. On this machine screw is a bronze nut that is attached to a block mounted horizontally in a plane at a right angle to the crimping rollers. This block is the center point for a scissors-jack type linkage that extends to each of the two non-stationary crimping roller blocks. The linkage is such that as the machine screw is rotated, the linkage center block moves along the screw to cause the non-stationary crimping roller blocks to slide in the direction perpendicular to the screw and thus change the depth of crimp.
Mounted on the opposite side of the machine screw is a universal joint which constitutes a coupling to a hydraulic motor. A linear encoder tracks the position of the center linkage block along the length of the machine screw and sends that information to a microprocessor. A rotary encoder tracks the length of panel that is being crimped by the apparatus and sends that information to the microprocessor. The rotation of the hydraulic motor that controls the depth of crimp is controlled by a valve that is controlled by the microprocessor. The microprocessor determines when to adjust the crimping rollers and to what depth based on the information received from the encoders.
Each shaft that supports the crimping rollers also supports a gear that fits into a drive train. This drive train is driven by a hydraulic motor separate from the motor that adjusts the crimping depth. The drive train motor controls the rotary motion of both the side crimping rollers and the main crimping rollers, and is also controlled by the microprocessor.